CN115575518A - Soil free gas discharge flux monitoring system for micro-leakage of coal bed gas in goaf - Google Patents
Soil free gas discharge flux monitoring system for micro-leakage of coal bed gas in goaf Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 73
- 239000003245 coal Substances 0.000 title claims abstract description 71
- 230000004907 flux Effects 0.000 title claims abstract description 46
- 238000012544 monitoring process Methods 0.000 title claims abstract description 25
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 84
- 238000004088 simulation Methods 0.000 claims abstract description 71
- 238000012360 testing method Methods 0.000 claims abstract description 50
- 238000005070 sampling Methods 0.000 claims abstract description 21
- 238000007789 sealing Methods 0.000 claims description 18
- 239000011435 rock Substances 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 239000010440 gypsum Substances 0.000 claims description 6
- 229910052602 gypsum Inorganic materials 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 4
- 230000000704 physical effect Effects 0.000 claims description 4
- 239000006004 Quartz sand Substances 0.000 claims description 3
- 239000004115 Sodium Silicate Substances 0.000 claims description 3
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 3
- 239000010428 baryte Substances 0.000 claims description 3
- 229910052601 baryte Inorganic materials 0.000 claims description 3
- 239000000084 colloidal system Substances 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 239000008262 pumice Substances 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims 50
- 239000002680 soil gas Substances 0.000 claims 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 4
- 239000001569 carbon dioxide Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 30
- 238000005065 mining Methods 0.000 description 5
- 230000005856 abnormality Effects 0.000 description 4
- 239000004215 Carbon black (E152) Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
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Abstract
The invention discloses a monitoring system for the free gas discharge flux of soil with micro-leakage of coal bed gas in a goaf, wherein a goaf overlying stratum simulation system in the system is used for the goaf overlying stratum simulation system; the goaf coalbed methane O-shaped gas source simulation and control system in the system is used for simulating free coalbed methane in the goaf, providing a gas source and controlling the gas source pressure, the component concentration and the occurrence position; the sampling and testing device for testing the discharge flux of soil layer micro-leakage gas in the system is used for collecting a gas sample micro-leaked to surface soil, so that the concentration and the discharge flux of free gas components in the soil can be conveniently tested; the system can realize indoor simulation of micro-leakage of the coal bed gas of the underground coal goaf under the conditions of different gas pressures, methane concentrations, occurrence space positions and the like, and samples and tests the concentrations of free gas methane and carbon dioxide in the surface soil and the discharge flux.
Description
Technical Field
The invention relates to the field of monitoring of soil free gas discharge flux of micro-leakage of coal bed gas in a goaf, in particular to a monitoring system of soil free gas discharge flux of micro-leakage of coal bed gas in a goaf.
Background
The phenomenon of methane or light hydrocarbon micro-leakage exists on the surface layer of the solid earth, if light hydrocarbon micro-leakage exists on the near-surface of most of known oil and gas reservoirs at home and abroad, the oil and gas geochemical exploration is to utilize the light hydrocarbon micro-leakage of the underground oil and gas reservoir to form geochemical anomaly on the near-surface, and define and identify the underground oil and gas reservoir. The phenomenon of micro-leakage of the coal bed gas in the mined-out area of the underground coal mine is found on the ground surface of a plurality of coal mine areas such as Poland and Czech, and the phenomenon of micro-leakage of the coal bed gas can also form geochemical abnormalities in soil on the ground surface, including the concentration and the discharge flux of free gas methane, carbon dioxide and the like of the soil. However, the micro-leakage of the coal bed gas in the underground goaf formed by the underground coal mine in China is not taken into consideration by the academic and industrial circles, and the related reports of the micro-leakage of the coal bed gas in the underground goaf are not disclosed in the public reports.
After the goaf is formed, an overflow zone, a (fracture) fracture zone and a bending subsidence zone are formed in the vertical direction of the overlying stratum, mining fracture O-shaped rings are formed on the plane, and free coal bed gas desorbed by mining pressure relief is enriched in the mining fracture O-shaped rings on the plane. Partial component molecules enriching coal bed gas in the O-shaped ring of the underground mining-induced fracture relatively and quickly move to the earth surface through the overlying rock stratum in a colloid-sized micro-bubble mode, the micro-bubbles penetrate through the overlying coal rock stratum and the aquifer of the goaf in an approximately vertical mode, namely micro-leakage, and the micro-leakage gas can form geochemical abnormalities such as free gas components in earth surface soil, free gas discharge flux and the like in the earth surface soil. The geochemical abnormal position and the abnormal index in the surface soil are closely related to occurrence characteristics of the coal bed gas in the goaf, but no related indoor experimental device exists at present, the occurrence forms (such as gas pressure, methane concentration and occurrence space position) of the coal bed gas in the goaf can be simulated, and the response relation of the occurrence characteristics of the coal bed gas in the goaf and the geochemical abnormalities such as free gas components and discharge capacity flux of the surface soil is analyzed under the condition of micro-leakage of the coal bed gas in the goaf.
Disclosure of Invention
Aiming at the technical defects, the invention aims to provide a soil free gas discharge flux monitoring system for micro-leakage of coal bed gas in a goaf, which can realize indoor simulation of micro-leakage of coal bed gas in an underground coal goaf under the conditions of different gas pressures, methane concentrations, occurrence space positions and the like, and sample and test the concentrations of methane and carbon dioxide in free gas of earth surface soil and discharge flux.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention provides a system for monitoring the discharge flux of free gas in soil with micro-leakage of coal bed gas in a goaf, which is used for simulating the micro-leakage process of the coal bed gas in an underground goaf from an overlying stratum to a near-surface soil layer and sampling and analyzing the micro-leakage gas in the surface soil layer, and is characterized in that: the device comprises a goaf overlying stratum simulation system, a goaf coalbed methane O-shaped gas source simulation and control system and a soil layer micro-leakage gas discharge flux test sampling device;
the goaf overlying stratum simulation system is used for a goaf overlying stratum simulation system and comprises a stratum simulation bin and a simulated stratum, wherein the simulated stratum is filled in the stratum simulation bin;
the goaf coalbed methane O-shaped gas source simulation and control system is used for simulating goaf free coalbed methane, providing a gas source, controlling the pressure, the component concentration and the occurrence position of the gas source, and comprises an O-shaped simulation fracture ring and a gas source control device, wherein the O-shaped simulation fracture ring is arranged at the bottom of the simulated stratum, and the gas source control device is arranged outside a stratum simulation bin and is communicated with the O-shaped simulation fracture ring through a pipeline;
the soil layer micro-leakage gas emission flux testing sampling testing device is placed at the top of a simulated stratum and used for collecting a gas sample micro-leaked to surface soil, and the concentration and the emission flux of free gas components in the soil can be conveniently tested.
Preferably, the simulated stratum is sequentially filled from bottom to top according to the column shape of the overlying stratum of the goaf, and the simulated rock stratum, the simulated coal seam and the soil layer are sequentially filled from bottom to top.
Preferably, the soil layer micro-seepage gas emission flux test sampling system comprises a plurality of test cavities, the bottom of each test cavity is open and is placed in the simulated formation, the top of each test cavity is provided with a gas outlet and a detachable sealing rubber plug, and the gas outlet is used for collecting gas by a gas collector.
Preferably, the stratum simulation bin is of a cubic structure, the bottom surface, the four side surfaces and the connected side surfaces of the stratum simulation bin are subjected to sealing treatment, the top of the stratum simulation bin is open, in order to prevent gas from overflowing from gaps between the simulated stratum and the stratum simulation bin, colloid sealing layers are coated between the periphery of the simulated stratum and the stratum simulation bin, and a soil layer at the top of the simulated stratum is in an open state.
Preferably, the simulated rock stratum and the simulated coal bed in the simulated stratum are manufactured by using similar materials according to the physical properties of overlying rock strata and coal beds of goafs on the basis of a similar principle, the manufacturing materials of a framework in the simulated rock stratum comprise quartz sand, barite and pumice powder, and the cementing agent comprises water gypsum and sodium silicate; the manufacturing material of the skeleton in the simulated coal seam comprises coal powder and sand, and the cementing agent adopts gypsum.
Preferably, the gas source control device comprises a gas cylinder, and an outlet of the gas cylinder is sequentially connected with the switch valve, the pressure constant valve, the pressure gauge, the gas storage valve, the gas storage bin, the gas sample acquisition controller, the pressure gauge, the gas inlet valve and the O-shaped simulated slit ring through pipelines.
Preferably, the O-shaped simulated fracture ring comprises a cross rod and a hollow annular pipeline, four ends of the cross rod are respectively fixed with four edges of the annular pipeline to form a Chinese character tian shape, a plurality of air outlet sieve holes communicated with an inner cavity of the annular pipeline are arranged on the annular pipeline, and the inner cavity of the annular pipeline is communicated with an air bottle in the air source control device through a pipeline.
The invention also provides a monitoring method of the monitoring system for the free gas discharge flux of the soil with the slightly leaked coal bed gas in the goaf, which comprises the following steps:
s1, preparing a goaf coalbed methane gas source according to the coalbed methane gas components and the concentration of the coal mine goaf, and filling the goaf coalbed methane gas source into a gas cylinder;
s2, gas filling of the gas storage bin is completed by using a gas cylinder, and the injection pressure is the actual coal mine goaf coal bed gas pressure;
s3, after gas filling of the gas storage bin is completed, closing the gas storage valve, opening the gas inlet valve, and enabling gas to flow into the O-shaped simulation fracture ring;
s4, arranging a plurality of testing cavities on the soil layer after the pressure of the pressure gauge is reduced by 0.1MPa, and covering the soil layer with sampling points;
s5, placing the test cavity with the sealing rubber plug removed into the position 10-30mm below the surface of the soil layer, and allowing gas to flow into the test cavity;
s6, after 3-5min, sealing the test cavity by using a sealing rubber plug, and collecting a gas sample by using a gas collector to penetrate through the sealing rubber plug and extend into the test cavity;
and S7, extracting a gas sample to a gas sample bottle in the test cavity by using a gas collector according to a preset time interval, measuring gas components and concentration in the sample by using a gas chromatograph, obtaining a change curve of the gas concentration along with sampling time, and calculating the gas components and the emission flux.
Preferably, the time intervals set in step S7 are 0min,2min,4min,8min,10min and so on.
The invention has the beneficial effects that:
(1) The goaf overlying stratum simulation system provided by the invention provides geological conditions of goaf coalbed methane micro-leakage by arranging a simulated stratum in the stratum simulation bin, so that the building of a goaf overlying stratum model is realized;
(2) The goaf coal bed gas O-shaped gas source simulation and control system simulates the occurrence states of the coal bed gas of the key goafs such as gas pressure, component concentration, occurrence positions and the like, and provides controllable and monitored experimental conditions;
(3) The soil layer micro-leakage gas discharge flux testing and sampling device can obtain soil layer gas samples of the goaf, which are slightly leaked to the earth surface at different plane positions and different time periods, so as to test and analyze the discharge flux and the free gas component concentration.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a system for monitoring soil free gas discharge flux of coal bed methane microleakage in a goaf according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an O-shaped simulated slit ring provided by an embodiment of the invention;
fig. 3 is a schematic installation diagram of a test chamber according to an embodiment of the present invention.
Description of reference numerals:
1. a gas cylinder; 2. an on-off valve; 3. a pressure-constant valve; 4. a pressure gauge; 5. a pipeline; 6. a gas storage valve; 7. a gas storage bin; 8. a gas sample collection controller; 9. a pressure gauge; 10. an intake valve; 11. an O-shaped simulated fracture ring; 12. a stratum simulation bin; 13. simulating a rock stratum; 14. simulating a coal seam; 15. a soil layer; 16. a test chamber; 17. sealing the rubber plug; 18. a gas collector; 19. air outlet sieve pores; 20. a cross bar.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
As shown in figures 1 to 3, the system for monitoring the free gas discharge flux of the slightly leaked soil of the coalbed methane in the goaf is used for simulating the slightly leaking process of the coalbed methane in the underground goaf from an overlying stratum to a soil layer near the surface and sampling and analyzing the slightly leaked gas in the soil layer at the surface,
the method comprises the steps of firstly obtaining experimental background information, such as the columnar overlying strata of a coal mine goaf, the physical properties (such as lithology, rock mechanical properties, pore parameters and the like) of a main rock stratum, the coal bed gas pressure of the coal mine goaf, the gas component concentration and the like, and collecting a near-surface soil sample overlying the coal mine goaf;
the system comprises a goaf overlying stratum simulation system, a goaf coalbed methane O-shaped gas source simulation and control system and a soil layer micro-leakage gas discharge flux test sampling device;
the goaf overlying stratum simulation system is used for a goaf overlying stratum simulation system and comprises a stratum simulation bin 12 and a simulated stratum, wherein the simulated stratum is filled in the stratum simulation bin;
the simulated stratum is sequentially filled from bottom to top according to the column shape of the overlying stratum of the goaf, and the simulated rock stratum 13, the simulated coal seam 14 and the soil layer 15 are sequentially filled from bottom to top.
The total thickness of the simulated stratum is 1.4m, and the thickness of the soil layer 15 is 0.4m; and simulating a soil layer 15 in the stratum, and filling the soil layer with the near-surface soil collected from the goaf of the coal mine.
The simulated rock stratum 13 and the simulated coal seam 14 in the simulated stratum are manufactured by using similar materials according to the physical properties of overlying rock strata and coal seams of goafs on the basis of a similar principle, the manufacturing materials of a framework in the simulated rock stratum 13 comprise quartz sand, barite and pumice powder, and the cementing agent comprises water gypsum and sodium silicate; the manufacturing materials of the framework in the simulated coal seam 14 comprise coal powder and sand, and the cementing agent adopts gypsum.
The stratum simulation bin is of a cubic structure, the bottom surface, the four side surfaces and the connected side surfaces of the stratum simulation bin are all sealed, the top of the stratum simulation bin 12 is open, in order to prevent gas from overflowing from gaps between the simulated stratum and the stratum simulation bin 12, colloid sealing layers are coated between the periphery of the simulated stratum and the stratum simulation bin 12, and a soil layer 15 at the top of the simulated stratum is in an open state.
The goaf coalbed methane O-shaped gas source simulation and control system is used for simulating goaf free coalbed methane, providing a gas source, controlling the gas source pressure, the component concentration and the occurrence position, and comprises an O-shaped simulation fracture ring 11 and a gas source control device, wherein the O-shaped simulation fracture ring 11 is arranged at the bottom of the simulated stratum, and the gas source control device is positioned outside a stratum simulation bin 12 and is communicated with the O-shaped simulation fracture ring 11 through a pipeline;
the sampling and testing device for testing the soil layer micro-leakage gas emission flux is placed at the top of the simulated stratum and used for collecting a gas sample micro-leaked to surface soil, so that the concentration and the emission flux of free gas components in the soil can be conveniently tested.
Soil layer micro-permeability gas discharges flux test sampling system includes a plurality of test cavity 16, and test cavity 16 diameter 50mm, 16 bottom openings of test cavity are put into in the simulation stratum, 16 tops of test cavity are equipped with the venthole and are equipped with detachable sealed plug 17, the venthole is used for gas collector 18 to gather gas.
The air source control device comprises an air bottle 1, wherein an outlet of the air bottle 1 is sequentially connected with a switch valve 2, a pressure constant valve 3, a pressure gauge 4, an air storage valve 6, an air storage bin 7, an air sample collection controller 8, a pressure gauge 9, an air inlet valve 10 and an O-shaped simulated slit ring 11 through a pipeline 5.
The gas storage bin 7 is a high-pressure-resistant sealed gas bin and is used for providing stable gas sources with fixed volumes under different pressures, and the gas storage bin is combined with a pressure gauge 9 and is used for monitoring gas pressure change formed by coal bed gas escape in a goaf;
the O-shaped simulated fracture ring 11 comprises a cross rod 20 and a hollow annular pipeline, four ends of the cross rod 20 are respectively fixed with four sides of the annular pipeline to form a Chinese character tian shape, a plurality of air outlet sieve holes 19 communicated with an inner cavity of the annular pipeline are arranged on the annular pipeline, and the inner cavity of the annular pipeline is communicated with a gas cylinder 1 in a gas source control device through a pipeline 5.
In the embodiment, the size of the O-shaped simulation fracture ring 11 is 50 multiplied by 50cm, 12 air outlet sieve holes are arranged on an annular pipeline of the O-shaped simulation fracture ring 11, the diameter of each air outlet sieve hole is 2.0cm, the O-shaped simulation fracture ring 11 is arranged at the lower part of a simulated stratum, the distance from the O-shaped simulation fracture ring 11 to the bottom surface of a stratum simulation bin 12 is 10cm, the O-shaped simulation fracture ring 11 is used for simulating a mining fracture O-shaped ring, and a simulated goaf free coal bed methane enrichment area is formed after ventilation.
The invention also provides a monitoring method of the monitoring system for the free gas discharge flux of the soil with the slightly leaked coal bed gas in the goaf, which comprises the following steps:
s1, preparing a goaf coalbed methane gas source according to the coalbed methane gas components and the concentration of the coal mine goaf, and filling the goaf coalbed methane gas source into a gas cylinder 1;
s2, gas filling of the gas storage bin 7 is completed by using the gas cylinder 1, and the injection pressure is the actual coal mine goaf coal bed gas pressure;
s3, after the gas storage bin 7 is filled with gas, closing the gas storage valve 6, opening the gas inlet valve 10, and enabling the gas to flow into the O-shaped simulated fracture ring 11;
s4, when the pressure of the pressure gauge 9 is reduced by 0.1MPa, arranging a plurality of testing cavities 16 on the soil layer 15, and covering the soil layer 15 with sampling points;
s5, placing the testing cavity 16 with the sealing rubber plug 17 removed into the position 10-30mm below the surface of the soil layer 15, and allowing gas to flow into the testing cavity 16;
s6, after 3-5min, sealing the test cavity 16 by using a sealing rubber plug 17, and collecting a gas sample by using a gas collector 18 to penetrate through the sealing rubber plug 17 and extend into the test cavity 16;
s7, extracting a gas sample into a gas sample bottle in the testing cavity 16 by using the gas collector 18 according to a preset time interval, measuring gas components and concentrations such as CH4 and CO2 in the sample by using a gas chromatograph, obtaining a change curve of the gas concentration along with sampling time, and calculating the emission flux of the gas components such as CH4 and CO 2.
In the step S7, the time intervals are set to be 0min,2min,4min,8min and 10min in sequence.
The invention realizes the real simulation of the overlying geologic body of the coal mine goaf. The goaf coal bed gas O-shaped gas source simulation and control system simulates the occurrence states of the coal bed gas of the key goafs such as gas pressure, component concentration, occurrence positions and the like, and provides controllable and monitored experimental conditions; soil layer microleakage gas discharges flux test sampling device can gather the little soil layer gas that leaks to the earth's surface in different plane positions, different time in collecting the gob coal bed gas to test analysis gas discharge flux, free gas component concentration. The method can analyze the response relationship between occurrence characteristics (such as gas pressure, methane concentration and occurrence space position) of the coal bed gas in the goaf and geochemical abnormality of the earth surface soil under the condition of micro leakage of the coal bed gas in the goaf.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. The utility model provides a little seepage's of collecting space area coal bed gas soil free gas discharge flux monitoring system for underground collecting space area coal bed gas passes the little seepage process simulation and the little seepage gas sampling analysis of earth's surface soil horizon of overburden stratum to nearly earth's surface soil horizon, its characterized in that: the device comprises a goaf overlying stratum simulation system, a goaf coalbed methane O-shaped gas source simulation and control system and a soil layer micro-leakage gas discharge flux test sampling device;
the goaf overlying stratum simulation system is used for a goaf overlying stratum simulation system and comprises a stratum simulation bin (12) and a simulated stratum, wherein the simulated stratum is filled in the stratum simulation bin;
the goaf coalbed methane O-shaped gas source simulation and control system is used for simulating goaf free coalbed methane, providing a gas source, controlling the gas source pressure, the component concentration and the occurrence position, and comprises an O-shaped simulation fracture ring (11) and a gas source control device, wherein the O-shaped simulation fracture ring (11) is arranged at the bottom of the simulated stratum, and the gas source control device is arranged outside the stratum simulation bin (12) and is communicated with the O-shaped simulation fracture ring (11) through a pipeline;
the sampling and testing device for testing the soil layer micro-leakage gas emission flux is placed at the top of the simulated stratum and used for collecting a gas sample micro-leaked to surface soil, so that the concentration and the emission flux of free gas components in the soil can be conveniently tested.
2. The system for monitoring the drainage flux of free soil gas from micro-leakage of coalbed methane in the goaf according to claim 1, wherein: the simulated stratum is sequentially filled from bottom to top according to the column shape of the overlying stratum of the goaf, and the simulated rock stratum (13), the simulated coal seam (14) and the soil layer (15) are sequentially filled from bottom to top.
3. The system for monitoring the drainage flux of free soil gas from micro-leakage of coalbed methane in the goaf according to claim 2, wherein: soil horizon micro-permeability gas discharges flux test sampling system includes a plurality of test cavity (16), test cavity (16) bottom opening is put into in the simulation stratum, test cavity (16) top is equipped with the venthole and is equipped with detachable sealed plug (17), the venthole is used for gas collector (18) to gather gas.
4. The system for monitoring the drainage flux of free soil gas from micro-leakage of coalbed methane in the goaf according to claim 1, wherein: the stratum simulation bin is of a cubic structure, the bottom surface, the four side surfaces and the side surfaces connected with the bottom surface are all sealed, the top of the stratum simulation bin (12) is open, in order to prevent gas from overflowing from gaps between the simulation stratum and the stratum simulation bin (12), colloid sealing layers are coated between the periphery of the simulation stratum and the stratum simulation bin (12), and a soil layer (15) at the top of the simulation stratum is in an open state.
5. The system for monitoring the drainage flux of free soil gas from micro-leakage of coalbed methane in the goaf according to claim 1, wherein: the simulated rock stratum (13) and the simulated coal seam (14) in the simulated stratum are manufactured by using similar materials according to the physical properties of overlying rock strata and coal seams of goafs on the basis of a similar principle, the manufacturing materials of a framework in the simulated rock stratum (13) comprise quartz sand, barite and pumice powder, and a cementing agent comprises water gypsum and sodium silicate; the manufacturing materials of the framework in the simulated coal seam (14) comprise coal powder and sand, and the cementing agent adopts gypsum.
6. The system for monitoring the soil free gas drainage flux of the micro leakage of the coalbed methane in the goaf according to claim 3, characterized in that: the gas source control device comprises a gas cylinder (1), wherein an outlet of the gas cylinder (1) is sequentially connected with a switch valve (2), a pressure constant valve (3), a pressure gauge (4), a gas storage valve (6), a gas storage bin (7), a gas sample acquisition controller (8), a pressure gauge (9), an air inlet valve (10) and an O-shaped simulated fracture ring (11) through a pipeline (5).
7. The system for monitoring the drainage flux of free soil gas from micro-leakage of coalbed methane in the goaf according to claim 1, wherein: the O-shaped simulated fracture ring (11) comprises a cross rod (20) and a hollow annular pipeline, four ends of the cross rod (20) are respectively fixed with four edges of the annular pipeline to form a field shape, a plurality of air outlet sieve holes (19) communicated with the inner cavity of the annular pipeline are formed in the annular pipeline, and the inner cavity of the annular pipeline is communicated with an air bottle (1) in an air source control device through a pipeline (5).
8. The monitoring method of the system for monitoring the free gas discharge flux of the soil with the micro-leakage of the coalbed methane in the goaf according to claim 6, is characterized by comprising the following steps:
s1, preparing a goaf coalbed methane gas source according to the coalbed methane gas components and the concentration of the coal mine goaf, and filling the goaf coalbed methane gas source into a gas cylinder (1);
s2, gas filling of the gas storage bin (7) is completed by using the gas cylinder (1), and the injection pressure is the actual coal mine goaf coal bed gas pressure;
s3, after the gas storage bin (7) is filled with gas, closing the gas storage valve (6), opening the gas inlet valve (10), and enabling the gas to flow into the O-shaped simulated fracture ring (11);
s4, arranging a plurality of testing cavities (16) on the soil layer (15) after the pressure of the pressure gauge (9) is reduced by 0.1MPa, and covering the soil layer (15) with sampling points;
s5, placing the testing cavity (16) with the sealing rubber plug (17) removed below the surface of the soil layer (15) by 10-30mm, and allowing gas to flow into the testing cavity (16);
s6, after 3-5min, sealing the test cavity (16) by using a sealing rubber plug (17), and collecting a gas sample by using a gas collector (18) to penetrate through the sealing rubber plug (17) and extend into the test cavity (16);
s7, extracting a gas sample to a gas sample bottle in the testing cavity (16) by using a gas collector (18) according to a preset time interval, measuring gas components and concentration in the sample by using a gas chromatograph, obtaining a change curve of the gas concentration along with sampling time, and calculating the gas components and the emission flux.
9. The monitoring method of the system for monitoring the discharge flux of the free gas in the soil with the micro leakage of the coalbed methane in the goaf as claimed in claim 8, wherein the time interval set in the step S7 is 0min,2min,4min,8min,10min and so on.
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